It is known to use spray nozzles to produce a spray for a wide variety of industrial applications including, for example, coating a surface with a liquid. Typically, in a spray nozzle coating application, liquid is atomized by the spray nozzle into a mist or spray of droplets which is directed and deposited onto a surface or substrate to be coated. The actual droplet size of the atomized liquid and the shape or pattern of the spray discharged from the nozzle can be selected depending upon a variety of factors including the size of the object being coated and the liquid being atomized. Other applications for nozzles may include cooling applications or mixing of gases.
One known technique for atomizing liquids into droplets is to direct pressurized gas such as air into a liquid and thereby mechanically break the liquid down into droplets. In such gas atomization techniques, it can be difficult to control and/or minimize the size and consistency of the droplets. Another known type of spray nozzle is an ultrasonic atomizing nozzle assembly that utilizes ultrasonic energy to atomize a liquid into a cloud of small, fine droplets which is almost smoke-like in consistency. However, because of the fine size of the droplets and mist-like consistency of the atomized droplets, it can be difficult to control and direct them as a spray towards the surface to be coated. Moreover, because the fine droplets have little mass, the droplets may drift or become thinly dispersed shortly after discharge from the spray nozzle. The uniformity and/or distribution of the droplets within a pattern may be difficult to control and may deteriorate rapidly after discharge from the nozzle assembly making it difficult to coat a surface evenly. Because ultrasonically produced spray patterns made up of such fine droplets are difficult to shape and control, their use in many industrial applications is disadvantageously affected.